Wireless power transmitter and method of error detection during use thereof

ABSTRACT

A wireless power transmitter is provided for power transmission to a wireless power receiver. The transmitter comprises a primary coil to transfer power to a secondary coil of the wireless power receiver, a power supply, a driver to provide an electric potential from the power supply to the primary coil, a monitoring system to measure electrical flow parameters of the primary coil, and to filter the measured electrical flow parameters thereby producing a response signal, and a controller to direct operation of the wireless power transmitter. The controller is configured to perform error checking by directing the driver to provide the electric potential as a superposition of a transmission signal and a sensing signal, the filter characteristics comprising electrical flow parameters of the and sensing signal, and detecting, based a difference between the response and sensing signals, an error condition indicative of a foreign object.

FIELD OF THE INVENTION

The present invention relates to a system and method for monitoringefficiency and controlling power transfer across a wireless powercoupling.

BACKGROUND OF THE INVENTION

Wireless power coupling allows electrical energy to be transferred froma power supply to an electric load without connecting wires. A powersupply is wired to a primary coil and an oscillating electric potentialis applied across the primary coil which induces an oscillating magneticfield therearound. The oscillating magnetic field may induce anoscillating electrical current in a secondary coil, placed close to theprimary coil. In this way, electrical energy may be transmitted from theprimary coil to the secondary coil by electromagnetic induction withoutthe two coils being conductively connected. When electrical energy istransferred inductively from a primary coil to a secondary coil, thepair are said to be inductively coupled. An electric load wired inseries with such a secondary coil may draw energy from the power sourcewhen the secondary coil is inductively coupled to the primary coil.

Leaks may arise if a foreign object, for example one which is metallicand/or magnetic, is located between the primary and secondary coilsduring charging. Besides inefficiencies which may arise owing to lostenergy, the presence of a foreign object within an inductive couple mayresult in parasitic heating, thereby posing a hazard.

SUMMARY OF THE INVENTION

According to one aspect of the presently disclosed subject matter, thereis provided a wireless power transmitter for inductive powertransmission to a wireless power receiver, the wireless powertransmitter comprising:

a primary coil to transfer power to a secondary coil of the wirelesspower receiver;

a power supply;

a driver to provide an electric potential from the power supply to theprimary coil;

a monitoring system to measure electrical flow parameters of the primarycoil, and to filter the measured electrical flow parameters based on oneor more filter characteristics (i.e., signal processing is applied whichremoves the filter characteristics), thereby producing a responsesignal; and

a controller to direct operation of the wireless power transmitter;wherein the controller is configured to perform error checking by:

-   -   directing the driver to provide the electric potential as a        superposition of a transmission signal and a sensing signal, the        filter characteristics comprising electrical flow parameters of        one of the transmission and sensing signals; and    -   detecting, based a difference between one or more electrical        flow parameters of the response signal and of the other of the        transmission and sensing signals, an error condition indicative        of a foreign object between the primary and secondary coils.

The frequency of the sensing signal may be substantially different fromthe frequency of the transmission signal.

The filter characteristics may comprise electrical flow parameters ofthe transmission signal. Thus, when there is no error condition, theresponse signal is expected to be the same as the sensing signal.

The frequency of the sensing signal may be constant.

The controller may be configured to vary the frequency of thetransmission signal during the power transmission.

The controller may be further configured to facilitate, when the errorcondition is detected, interrupting the electrical potential to theprimary coil. This may comprise directing the driver to cease providingthe electric potential.

The controller may be configured to perform the error checking in anongoing manner during the power transmission.

The controller may be configured to perform the error checkingcontinuously during the power transmission.

The controller may be configured to perform the error checking atintervals during the power transmission.

The controller may comprise a comparator.

According to another aspect of the presently disclosed subject matter,there is provided a method of detecting an error condition, indicativeof a foreign object between a wireless power transmitter and a wirelesspower receiver, said wireless power transmitter comprising a primarycoil for transferring power wirelessly to a secondary coil of saidwireless power receiver, the method comprising:

-   -   providing an electric potential, being a superposition of a        transmission signal and a sensing signal, to the primary coil;    -   measuring electrical flow parameters of the primary coil;    -   filtering the measured electrical flow parameters based on one        or more filter characteristics (i.e., signal processing is        applied which removes the filter characteristics), thereby        producing a response signal;    -   comparing one or more electrical flow parameters of the response        signal with corresponding electrical flow parameters of one of        the transmission and sensing signals; and    -   determining, based on the comparing, whether or not the error        condition exists.

The frequency of the sensing signal may be substantially different fromthe frequency of the transmission signal.

The filter characteristics may comprise electrical flow parameters ofthe transmission signal. Thus, when there is no error condition, theresponse signal is expected to be the same as the sensing signal.

The frequency of the sensing signal may be constant.

The frequency of the transmission signal may vary during the powertransmission.

The method may further comprise, when the error condition is detected,interrupting the electrical potential to the primary coil.

The error checking may be performed in an ongoing manner during thepower transmission.

The error checking may be performed continuously during the powertransmission.

The error checking may be performed at intervals during the powertransmission.

The wireless power transmitter may further comprise a comparator.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the embodiments and to show how it may becarried into effect, reference will now be made, purely by way ofexample, to the accompanying drawings.

With specific reference now to the drawings in detail, it is stressedthat the particulars shown are by way of example and for purposes ofillustrative discussion of the preferred embodiments of the presentinvention only, and are presented in the cause of providing what isbelieved to be the most useful and readily understood description of theprinciples and conceptual aspects of the invention. In this regard, noattempt is made to show structural details of the invention in moredetail than is necessary for a fundamental understanding of theinvention; the description taken with the drawings making apparent tothose skilled in the art how the several forms of the invention may beembodied in practice. In the accompanying drawings:

FIG. 1 is a block diagram showing the main elements of a wireless powercoupling incorporating a signal transfer system according to a firstembodiment of the invention;

FIG. 2a-d show another embodiment of the signal transfer system in whicha control signal is transmitted through an inductive energy coupling;

FIG. 3 is a schematic diagram showing a signal transfer systemintegrated into a contactless wireless power coupling system forpowering a computer;

FIG. 4 is a flowchart showing a method for transferring a transmissionsignal through an inductive energy coupling in accordance with theinvention.

FIG. 5 is a block diagram representing another embodiment of the signaltransfer system incorporated into an efficiency monitor for monitoringthe efficiency of power transmission by a wireless power transmitter;

FIG. 6a is a schematic diagram of a wireless power transmitter with anelectrical load inductively coupled thereto, monitored by an efficiencymonitor;

FIG. 6b is a schematic diagram of the wireless power transmitter of FIG.6a wherein a power drain has been introduced between the primary andsecondary coils;

FIG. 7 is a flow diagram of a method for using the signal transfersystem to monitor the efficiency of power transmission by a wirelesspower transmitter;

FIG. 8 is a block diagram showing the main elements of a wireless powertransmitter and an associated wireless power receiver;

FIGS. 9 through 11 are flow diagram illustrating different foreignobject tests performed by the wireless power transmitter illustrated inFIG. 8;

FIG. 12 is a block diagram showing the main elements of another exampleof a wireless power transmitter and an associated wireless powerreceiver;

FIG. 13 is a flow diagram illustrating a foreign object test performedby the wireless power transmitter illustrated in FIG. 12; and

FIG. 14 is a schematic illustration of a wireless charging stationaccording to the presently disclosed subject matter.

DETAILED DESCRIPTION

Reference is now made to FIG. 1 showing a block diagram of the mainelements of a wireless power coupling 200 incorporating a signaltransfer system 100 according to a first embodiment of the invention;

The wireless power coupling 200 consists of a primary coil 220 and asecondary coil 260. The primary coil 220 is wired to a power supply 240typically via a driver 230 which provides the electronics necessary todrive the primary coil 220. Driving electronics may include a switchingunit providing a high frequency oscillating voltage supply, for example.The secondary coil 260 is wired to an electric load 280.

When the secondary coil 260 is brought into proximity with the primarycoil 220, the pair of coils forms an inductive couple and power istransferred from the primary coil 220 to the secondary coil 260. In thisway a power transmitter 210 may provide power to an electric device 290.

The signal transfer system 100 comprises: a signal generator 120, forgenerating a control signal S_(C); a signal transmitter 140 fortransmitting said control signal S_(C); and a signal receiver 160 forreceiving said control signal S_(C).

Although in the signal transfer system 100 described herein, the signaltransmitter 140 is incorporated into the power transmitter 210 and thesignal receiver 160 is incorporated into the electrical device 290, itwill be appreciated that a signal transmitter 140 may alternatively oradditionally be incorporated into the electrical device 290 and a signalreceiver 160 may alternatively or additionally be incorporated into thepower transmitter 210.

The control signal S_(C) communicates encoded data pertaining to thepower transmission. This data may be pertinent to regulating efficientpower transmission. Examples of such data includes parameters such as:required operating voltage, current, temperature or power for theelectric load 280, the measured voltage, current, temperature or powersupplied to the electric load 280 during operation, the measuredvoltage, current, temperature or power received by the electric load 280during operation and the like.

In other embodiments, the control signal S_(C) may communicate datarelating to the coordinates of the primary coil 220 for the purposes ofindicating the location of the power transmitter 210. Alternatively, thecontrol signal S_(C) may communicate data relating to the identity orpresence of the electric load 280 such as the location of the secondarycoil 260, or an identification code or the electric device 290 or itsuser.

Various signal transmitters 140 and signal receivers 160 may be usedwith the signal transfer system. Where the primary and secondary coils220, 260 are galvanically isolated for example, optocouplers may have alight emitting diode serving as a signal transmitter 140 which sendsencoded optical signals over short distances to a photo-transistor whichserves as a signal receiver 160. Optocouplers typically need to bealigned such that there is a line-of-sight between signal transmitterand signal receiver. In systems where alignment between the signaltransmitter 140 and signal receiver 160 may be problematic, optocouplingmay be inappropriate and alternative systems may be preferred such asultrasonic signals transmitted by piezoelectric elements or radiosignals such as Bluetooth, WiFi and the like. Alternatively the primaryand secondary coils 220, 260 may themselves serve as the signaltransmitter 140 and signal receiver 160.

Coil-to-coil Signal Transfer

One aspect of the present embodiments relate to a signal transfer systemfor transferring a transmission signal regarding an electric loadconnectable via an inductive energy coupling to a power source. Theinductive energy coupling comprises a primary coil connectable to thepower source in inductive alignment with a secondary coil connectable tothe electric load, the system comprises at least one ancillary load; atleast one switching unit comprising a modulator for modulating abit-rate signal with an input signal to create a modulated signal and aswitch for intermittently connecting the ancillary load to the secondarycoil according to the modulated signal; at least one current monitor formonitoring primary current drawn by the primary coil and producing aprimary current signal, and at least one correlator forcross-correlating the primary current signal with the bit-rate signalfor producing an output signal.

The switching unit preferably also comprises a controller configured toencode data into the input signal. Typically, the switching unit furthercomprises a frequency divider and the inductive energy couplingtransfers energy with a driving frequency and the bit rate frequency isan integer fraction of the driving frequency.

The inductive energy coupling is typically a device wherein the primarycoil is galvanically isolated from said secondary coil. The device mayinclude a transformer, a DC-to-DC converter, an AC-to-DC converter, anAC-to-AC converter, a flyback transformer, a flyback converter, afull-bridge converter, a half-bridge converter, a buck converter, aboost converter, a buck-boost converter, a SEPIC converter or a zetaconverter, for example.

Optionally, the input signal carries encoded data pertaining to, forexample, the presence of the electric load, required operating voltagefor the electric load, required operating current for the electric load,required operating temperature for the electric load, measured operatingvoltage for the electric load, measured operating current for theelectric load, measured operating temperature for the electric load,and/or a user identification code.

In one embodiment, a contactless inductive coupling is provided,comprising the signal transfer system wherein the primary coil isembedded in a power jack and the secondary coil is embedded in a powerplug galvanically isolated from the power jack.

An aspect of the technology described herein, teaches a method fortransferring a signal through an inductive energy coupling, wherein theinductive energy coupling comprises a primary coil connected to a powersource and a secondary coil connected to an electric load, the methodcomprising the following steps: providing an input signal, providing abit-rate signal, modulating the bit-rate signal with the input signal tocreate a modulated signal, connecting an ancillary load to the secondarycoil intermittently according to the modulated signal, monitoring aprimary current drawn by the primary coil and producing a primarycurrent signal; and cross-correlating the primary current signal withthe bit-rate signal to generate an output signal.

According to another aspect, a method for regulating power transferacross a contactless inductive coupling is taught wherein the outputsignal provides details of power requirements of the load. Typically theinput signal is provided by encoding data regarding at least one powerrequirement of the electric load into the input signal. Optionally andtypically, the power requirement depends on parameters such as operatingvoltage, operating current and/or operating temperature. Alternativelythe input signal is provided by monitoring at least one operatingparameter of the electric load and encoding monitored parameter datainto the input signal. Optionally the parameter is selected from thegroup comprising operating voltage, operating current and operatingtemperature. Typically the method for transferring a signal through aninductive energy coupling includes a preliminary step of detecting thepresence of an electric load.

Reference is now made to FIGS. 2a-d wherein a signal transfer system2100 according to a second general embodiment of the invention is shown.With particular reference to FIG. 2a , the signal transfer system 2100is configured to transmit a transmission signal through an inductiveenergy coupling 2200. The inductive energy coupling 2200 consists of aprimary coil L₁ which may be connected to a power source 2240 and asecondary coil L₂, galvanically isolated therefrom, across which anelectric load 2280 may be connected either directly or via an AC-DCconverter 2270.

A transmission circuit 2140 may be connected in parallel with theelectric load 2280. The transmission circuit 2140 comprises an ancillaryload 2142 connected to the secondary coil L₂ via a switching unit 2144.Typically the ancillary load 2142 is much smaller than the electric load2280.

A corresponding reception circuit 2160 is connected to the primary coilL₁ of the inductive energy coupling 2200 and comprises a current monitor2162, such as an ammeter in series with the primary coil L₁, and acorrelator 2164.

The switching unit 2144 is configured to receive an input signal and abit-rate signal F_(b). A modulator (not shown) modulates the bit-ratesignal F_(b) with the input signal S_(in) to produce a modulated signalS_(M). The ancillary load 2142 is intermittently connected to thesecondary coil L₂ at a rate determined by the modulated signal S_(M).

The power source 2240, such as an alternating-current voltage source,intermittent direct current voltage source or the like, is configuredand operable to produce a primary voltage V₁ which oscillates at adriving frequency F_(d). The oscillating primary voltage V₁ in coil L₁induces a secondary voltage V₂(t) in the secondary coil L₂. Thesecondary voltage V₂(t) is optionally passed through an AC-DC converter22 producing a direct-current voltage V₂₂(t).

The electric load 2280 which is coupled to the secondary coil L₂—eitherdirectly or via the AC-DC converter 2270—draws a load current 1 ₂₂. Thepower P₂₂ provided to the load 2280 is given by the scalar product ofthe voltage V₂₂ and the load current I₂₂. When the ancillary load 2144is connected, an additional ancillary current i₂₄ is also drawn. Thus,with the ancillary load 2144 connected, the total power P₂ drawn by thesecondary coil L₂ is given by:

P ₂(t)={right arrow over (V)}₂₂(t)[{right arrow over (I)}₂₂ +{rightarrow over (i)} ₂₄(t)]

where the ancillary current signal i₂₄(t) varies with the modulatedsignal S_(M).

The input power P₁(t) provided to the primary coil L₁ is given by:

P ₁(t)={right arrow over (V)}₁(t){right arrow over (I)} ₁₀(t)

where the primary voltage V_(i)(t) oscillates at the driving frequencyF_(d) which is determined by the power supply 2240.

Input power P₁(t) provided by the primary coil L₁ is generallyproportional to the total power P₂₂(t) drawn by the secondary coil L₂,and the primary voltage V₁(t) is determined by the power supply.Perturbations in the primary current I_(I0)(t) supplied to the primarycoil L₁ are thus in proportion with i₂₄(t).

The current monitor 2162 monitors the primary current I_(I0)(t) overtime, producing a primary current signal S_(p) which typically hassimilar characteristics to the modulated signal S_(M). The correlator2164 is configured to cross-correlate the primary current signal S_(p)with the bit rate F_(b). The output signal S_(out) of the correlator2164 therefore has the same characteristics as the input signal S_(in).

In this manner, information carried by the input signal S_(in) istransmitted from the transmission circuit 2140 and is retrievable by thereception circuit 2160 from the output signal S_(out). It is noted thatthe signal transfer system 2100 described herein, transmits atransmission signal across the same wireless power coupling 2200 as usedfor power transmission. This is in contradistinction to prior arttransmission systems, which use additional elements to provide signaltransmission channels separate from the power transmission channels. Inconsequence of this innovative approach, additional transmissionelements such as optocouplers, piezoelectric elements, supplementarycoil pairs and the like are not generally required.

With reference now to FIG. 2b , an exemplary transmission circuit 2140of the signal transfer system 2100 of FIG. 2a is shown. An AC-to-DCconverter 2270 comprising a diode 2272 and a capacitor 2274, which isconnected in parallel to the secondary coil L₂, converts an AC secondaryvoltage V₂ from the secondary coil L₂ into a DC load voltage V₂₂ whichis connected across an electric load 2280.

The connection between the ancillary load 2142 and the load voltage V₂is controlled by a switching unit 2144 which includes a frequencydivider 2145, microcontroller 2146 and a switch 2147. The frequencydivider 2145 provides the bit-rate signal F_(b) which is passed to themicrocontroller 2146. The microcontroller 2146 is configured to modulatethe bit-rate signal F_(b) according to input signals including controlsignals S_(C) from the electric load 2280 and external signals S_(E). asdescribed hereinbelow.

Control signals S_(C) may be used to regulate the power supply. Controlsignals S_(C) typically provide data relating to load parameters.Typically these include the required operating voltage, current andtemperature and the actual measured operating voltage, current andtemperature as monitored during operation of the load.

External Signals S_(E) may be used to provide the transmission circuit2140 with external data to be digitally encoded into the input signalS_(in) by the microcontroller 2146 and transmitted to the receptioncircuit 2160. External information, may, for example, provide usefulsupplementary data such as a user identification code, a pass key,battery level of the load device and the like.

It will be appreciated that the ability to transmit supplementaryinformation such as external signals S_(E) through the inductive energycoupling 2200 presents a further advantage over prior art systems whichare only suitable for transmitting control signals.

FIG. 2c shows a schematic representation of an exemplary receptioncircuit 2160 in accordance with the signal transfer system of FIG. 2a ,consisting of a current monitor 2162, a frequency divider 2166, acorrelator 2164 and a microcontroller 2168. The frequency divider 2166provides the bit-rate signal F_(b) which is typically an integerfraction of the driving frequency F_(d). The current monitor 2162provides a primary current signal S_(P) which is passed to thecorrelator 2164 for cross-correlation with the bit-rate signal F_(b).The resulting output signal S_(out) is passed to a microcontroller 2168which may use the output signal S_(out) to pass a control signal S_(C)to control the power source 2240 so as to regulate the power provided tothe electric load 2280. The microcontroller 2168 may also be used toextract external signals S_(E) from the output signal.

An exemplary use of the reception circuit 2160 of FIG. 2c is highlightedin FIG. 2d which shows the reception circuit 2160 configured to controla flyback power source 2240F. In a flyback converter, a direct currentvoltage source 2242 is intermittently connected to a primary coil L₁ bya switch 2244. This produces a varying voltage signal V₁(t) in theprimary coil L₁ which induces a secondary voltage V₂ in a secondary coilL₂ (FIG. 2a ). The secondary coil L₂ is generally connected to asmoothing circuit such the AC-DC converter 2270 shown in FIG. 2b toproduce a DC output.

The switch 2244 is controlled by a driver 2248 which receives a pulsingsignal F_(d) from a clock 2246. The pulsing signal F_(d) determines thefrequency with which the direct current voltage source 2242 is connectedto the primary coil L₁. The power delivered to the primary coil L₁ maybe regulated by varying the duty cycle of the switch 2244. The dutycycle is the proportion of the time between pulses during which theswitch 2244 is closed.

FIG. 2d shows the innovative use of the signal transfer system 2100which receives a feedback signal transferred between the primary andsecondary power transmission coils and received by the reception circuit2160. This is an improvement on prior art flyback converters, whereinadditional elements such as optocouplers or the like have been used totransmit feedback signals.

The microcontroller 2168 generates a control signal S_(c) which isrelayed to the driver 2248. The control signal S_(c) determines the dutycycle of the switch 2248 and so may be used to regulate powertransmission.

Although only a flyback converter is represented in FIG. 2d it is notedthat a control signal S_(c) thus transmitted may be used to regulatepower transfer in a variety of transmission assemblies such as atransformer, a DC-to-DC converter, an AC-to-DC converter, an AC-to-ACconverter, a flyback transformer, a full-bridge converter, a half-bridgeconverter or a forward converter for example.

As an example of the signal transfer system 100 (FIG. 1), with referenceto FIG. 3, according to a third embodiment of the invention, a signaltransfer system 3100 may be integrated into a contactless wireless powercoupling system 3200 where power is inductively transmitted from a jackunit 3212 to a plug unit 3292 galvanically isolated therefrom. Atransmission circuit 3140 embedded in the plug unit 3292 may be used totransmit control signals S_(C) to a reception circuit 3160 in the jack3212. Thus once the primary L₁ and secondary L₂ coils are aligned,control signals may be passed between the plug 3292 and jack 3212 unitswith no need to align additional components such as optocouplers, andthe like. Where a contactless plug 3292 is used, for example to power aportable computer 3290 having on-board power cells 3280, the signaltransfer system 3100 may be used to detect the presence of the load 3290producing a detection signal S_(DL) and then to provide the jack 3212with signals relating to the identity of the user S_(ID) and the serialnumber Ss_(N) or other identifier of the laptop computer 3290. Signalsregarding the operating voltage and current required by the PC may beprovided as a regulatory signal S_(Q) which may also providesupplementary information such as information related to the power levelof the cells 3280, for example. Using this signal S_(Q), the signaltransfer system 3100 may be used to select between powering the computer3290 directly, recharging the power cells 3280 thereof, or both poweringand recharging, depending on defaults and predetermined criteria. It isfurther noted that when used for recharging cells 3280, the ability tomonitor the temperature of the cells 3280 during recharging may be usedto prevent overheating.

Referring to FIG. 4, a flowchart showing a method for transferring atransmission signal through an inductive energy coupling in accordancewith another embodiment of the invention is presented. With furtherreference to FIG. 2a , an Input Signal S_(in)—Step (a) and a Bit-rateSignal F_(b)—Step (b) are provided to the transmission circuit 2140. TheBit-rate Signal F_(b) is then modulated by the Input Signal S_(in),producing a Modulated Signal S_(M)—Step (c). An ancillary load 2142 isthen connected to the second coil L₂ intermittently according to theModulated Signal S_(M)—Step (e). The reception circuit 2160 monitors theprimary current drawn by the primary coil L₁ to produce a PrimaryCurrent Signal S_(P)—Step (e). This Primary Current Signal S_(P) is thencross-correlated with the Bit-rate Signal F_(b) to generate an OutputSignal S_(out)—Step (f).

The basic signal transfer system and method described hereinabove arecapable of variation. For example, it will be appreciated that throughthe use of such a system, information regarding a load 2280 may betransmitted to the power transmitter 2210 across the inductor coils L₁and L₂ of the inductive coupling 2200, as a signal superimposed on thepower transmitted, without requiring additional data transmittingcomponents.

Power Coupling Efficiency

Embodiments of the invention are directed to providing methods formonitoring the efficiency of power transmission by a wireless powertransmitter comprising at least one primary coil wired to a powersupply, for inductively coupling with a secondary coil wired to anelectric device. The method comprises the steps of: measuring the inputpower delivered to the primary coil, measuring the output power receivedby the electric device, communicating the input power to a processor,communicating the output power to the processor and the processordetermining an index of power-loss.

In one specific application, the index of power-loss is an efficiencyquotient Q, being the ratio of the output power to the input power, andthe method comprises the further step of: disconnecting the primary coilfrom the power supply if the efficiency quotient Q is below a thresholdvalue. Typically the threshold efficiency quotient is in the range offrom 75% to 95%.

In another application, the index of power-loss is an efficiencydifferential Δ, being the difference between the output power to theinput power, and the method comprises the further step of: disconnectingthe primary coil from the power supply if the efficiency differential Δis above a threshold value.

A further aspect of the technology described herein relates to anefficiency monitor for monitoring the efficiency of power transmissionby a wireless power transmitter of the type including at least oneprimary coil wired to a power supply, for inductively coupling with asecondary coil wired to an electric device. The efficiency monitorincludes: at least one input power monitor for measuring the input powerdelivered to the primary coil; at least one output power monitor formeasuring the output power received by the secondary coil; at least oneprocessor for determining an index of power-loss; and at least onecommunication channel for communicating the input power and the outputpower to the processor.

Typically the efficiency monitor also includes at least onecircuit-breaker for disconnecting the primary coil from the powersupply. Preferably the input power monitor is incorporated within thepower transmitter and the output power monitor is incorporated withinthe electric device.

Optionally, the electric device comprises at least one signaltransmitter for transmitting the output power to a signal receiverincorporated in the wireless power transmitter. The signal transmittermay include one or more light emitting diodes, radio transmitters,optocouplers, or ancillary load transmitter circuits, for example.

According to preferred embodiments, the efficiency monitor includes oneor more hazard detectors in communication with the processor. Suchhazard detectors may include magnetic sensors, heat sensors,electromagnetic radiation sensors and Hall probes, for example

Reference is now made to FIG. 5 showing a block diagram of a signaltransfer system 4100. The signal transfer system 4100 is incorporatedinto an efficiency monitor 4300 for monitoring the efficiency of powertransmission by a wireless power transmitter 4210.

The wireless power transmitter 4210 consists of a primary coil 4220wired to a power supply 4240 via a driver 4230 which provides theelectronics necessary to drive the primary coil 4220. Drivingelectronics may include a switching unit providing a high frequencyoscillating voltage supply, for example

If a secondary coil 4260 is brought into proximity with the primary coil4220, the pair of coils forms an inductive couple, and power istransferred from the primary coil 4220 to the secondary coil 4260. Inthis way the power transmitter 4210 may provide power to an electricdevice 4262 comprising an electric load 4280 wired in series with thesecondary coil 4260.

The efficiency monitor 4300 consists of an input power monitor 4122incorporated within the power transmitter 4210 and an output powermonitor 4124 incorporated within the electric device 4290, both incommunication with a processor 4162.

The input power monitor 4122 is configured to measure the input powerP_(in) provided by the primary coil 4220 and communicates this value tothe processor 4162.

The output power monitor 4124 is configured to measure the output powerP_(out) received by the secondary coil 4260 and communicates this valueto the processor 4162.

The processor 4162 is configured to receive the values of the inputpower P_(in) and the output power P_(out) and to calculate an index ofpower-loss. The index of power loss indicates how much power is leakingfrom the inductive couple. The index of power-loss may be the efficiencyquotient Q which is the ratio between them, P_(out)/P_(in), which is anindication of the efficiency of the inductive coupling. Alternativelythe index of power loss may be the efficiency differential Δ which isthe difference between P_(out) and P_(in).

The processor 4162 may additionally or alternatively be configured totrigger a circuit-breaker 4280 thereby cutting off the primary coil 4220from the power supply 4240 when the efficiency quotient Q falls below apredetermined threshold or the efficiency differential Δ rises above apredetermined threshold. Typically, this predetermined threshold for theefficiency quotient Q is in the range of from about 75% to 95%, and morepreferably about 85%.

With reference to FIG. 6a , an efficiency monitor 5300 for a wirelesspower transmitter 5210 is shown. wireless power transmitter 5210consists of a primary coil 5220 wired to a power source 5240 via anefficiency monitor 5300 all concealed behind a facing layer 5642 of ahorizontal platform 5640 such as a desk-top, a kitchen work-top, aconference table or a work bench. The facing layer may be a sheet ofself-adhesive plastic film, plastic, vinyl, Formica or wood veneer, forexample.

In other embodiments a primary coil 5220 may be concealed beneath orwithin flooring such as rugs, fitted carpet, parquet, linoleum, floortiles, tiling, paving and the like. Alternatively the primary coil 5220may be concealed behind or within a vertical surface such as a wall of abuilding or a cabinet, for example behind wallpaper or stretched canvasor the like.

The primary coil 5220 may be used to power an electrical device 5290such as a computer wired to a secondary coil 5260. The electrical device5290 is placed upon the surface 5642 of a platform 5640 such that thesecondary coil 5260 is aligned with the primary coil 5220 therebeneath.

The efficiency of the power transmitter 5210 is monitored by anefficiency monitor 5300. An input power monitor 5122 is incorporatedwithin the power transmitter 5210 behind the platform 5640 and is indirect conductive communication with a processor 5162. An output powermonitor 5124 is incorporated within the electrical device 5290 and isnot physically connected to the power transmitter 5210. The output powermonitor 5124 communicates with the processor 5162 via a signal transfersystem 5100 comprising a signal transmitter 5140 incorporated within theelectrical device 5290 which is configured to transmit a signal to asignal receiver 5160 incorporated within the power transmitter 5210.

The signal transmitter 5140 may be a standard signal transmitter such asthose widely used in computing and telecommunications, such as anInfra-red, Wi-fi or Bluetooth transmitter or the like. Indeed, any lightemitting diodes, radio transmitters, optocouplers or other suchtransmitters of radiation for which the platform 5640 is translucent maybe used. Alternatively a fiber optic pathway may be provided through theplatform.

In certain embodiments, an optical transmitter, such as a light emittingdiode (LED) for example, is incorporated within the power transmitter5210 and is configured and operable to transmit electromagneticradiation of a type and intensity capable of penetrating the casing ofthe electrical device 5290, and the surface layer 5642. An opticalreceiver, such as a photodiode, a phototransistor, a light dependentresistors of the like, is incorporated within the primary unit forreceiving the electromagnetic radiation transmitted through the surfacelayer 5642.

It is noted that many materials are partially translucent to infra-redlight. It has been found that relatively low intensity infra red signalsfrom LEDs and the like, penetrate several hundred microns of commonmaterials such as plastic, cardboard, Formica or paper sheet, to asufficient degree that an optical receiver, such as a photodiode, aphototransistor, a light dependent resistors or the like, behind a sheetof from 0.1 mm to 2 mm of such materials, can receive and process thesignal. For example a signal from an Avago HSDL-4420 LED transmitting at850 nm over 24 degrees, may be detected by an Everlight PD15-22C-TR8 NPNphotodiode, from behind a 0.8 mm Formica sheet. For signalling purposes,a high degree of attenuation may be tolerated, and penetration of only asmall fraction, say 0.1% of the transmitted signal intensity may besufficient. Thus an infra-red signal may be used to provide acommunication channel between primary and secondary units galvanicallyisolated from each other by a few hundred microns of wood, plastic,Formica, wood veneer, glass or the like.

The signal transmitter 5140 and signal receiver 5160 may be laterallydisplaced from the primary coil 5220 and secondary coil 5260. Inpreferred embodiments, however, the signal transmitter 5140 is locatedat the center of the secondary coil 5260 and the signal receiver 5160 islocated at the center of the primary coil 5220. This permits alignmentto be maintained through 360 degree rotation of the secondary coil 5260relative to the primary coil 5220.

The processor 5162 is configured to receive the values of the inputpower P_(in), directly from the input power monitor 5122, and the outputpower P_(out), via the signal receiver 5160. The processor 5162 thencalculates the efficiency quotient Q. In normal usage as represented inFIG. 6a , the processor records an efficiency quotient Q higher than apredetermined threshold so power transmission continues uninterrupted.When the efficiency quotient Q falls below a predetermined threshold,this indicates that power is being drawn from the primary coil 5220 bysome power drain other than the secondary coil 5260.

FIG. 6b is a schematic diagram of the wireless power transmitter 5210 ofFIG. 6a wherein a power drain such as a conductive sheet of metallicfoil 5800 is introduced between the primary coil 5220 and the secondarycoil 5260. The oscillating magnetic field produced by the primary coil5220 when connected to a high frequency oscillating voltage from adriver 5230, produces eddy currents in the conductive sheet 5800 therebyheating the conductive sheet and draining power from the primary coil5220. Such a power drain may be wasteful and/or dangerous. It will beappreciated that leak prevention systems which cut off power to theprimary coil 5220 if no secondary coil 5260 is coupled thereto, wouldfail to detect this hazard.

In contradistinction to previous systems known to the inventors,embodiments of the present invention measure the efficiency quotient Q.Consequently, when a power drain is introduced, such as that shown inFIG. 6b , for example, the output power P_(out) received by thesecondary coil 5260 is lower than normal and the efficiency quotient Qmay therefore drop below the predetermined threshold. The efficiencymonitor 5300 is thus able to detect the hazard.

According to certain embodiments, additional detectors (not shown) maybe incorporated within the power transmitter 5210, the platform 5640 orthe electrical device 5290 for monitoring other scientific effects whichmay be indications of possible hazards such as the magnetic fieldgenerated by the primary coil 5220, or the temperature of the platform5640 for example. Such detectors may function in accordance with one ormore of a variety of principles, including, inter alia, magnetic sensingmeans, Hall probes, heat sensors or electromagnetic sensors.

The processor 5162 may assess the level of the hazard detected byprocessing the various signals received according to a predeterminedlogical sequence. If necessary, the processor 5162 may trigger acircuit-breaker 5280 thereby cutting off the primary coil 5220 from thepower supply 5240. Depending on the nature of the hazard, the processor5162 may additionally or alternatively alert a user to the hazard. Thealert may be a visual or audio alarm for example, such as a buzzer orlight incorporated in the power transmission surface, or a signal sentto the computer 5290 which displays a warning 5294 on its visual display5296 or emits a warning sound.

In preferred embodiments the output power P_(out) may be monitored andencoded into the input signal S_(in). The coil-to-coil signal generatorshown in FIG. 2a may be used to transmit the input signal S_(in) from atransmission circuit 2140 (FIG. 2a ) incorporated within an electricaldevice 290 (FIG. 1) and is retrievable by the reception circuit 2160(FIG. 2a ) incorporated within the power transmitter 210 (FIG. 1) fromthe output signal S_(out). The retrieved signal may then be communicatedto a processor which uses it to calculate the efficiency quotient Q.

Reference is now made to FIG. 7 showing a flow diagram of a method formonitoring the efficiency of power transmission by a wireless powertransmitter according to a further embodiment of the present invention.The method includes the following steps:

-   -   a) measuring the input power delivered to a primary coil;    -   b) measuring the output power received by an electric device;    -   c) communicating the input power P_(in) to a processor;    -   d) communicating the output power P_(out) to the processor;    -   e) determining an index of power-loss, such as an efficiency        quotient Q or efficiency differential Δ;    -   f) optionally, disconnecting the primary coil from the power        supply, for example if the efficiency quotient Q is below a        threshold value (f1) or the efficiency differential Δ is above a        threshold value (f2), thereby preventing power leakage.

As illustrated in FIG. 8, a wireless power transmitter, which isgenerally indicated at 7000, is provided. The wireless power transmitter7000 is configured to transmit power (e.g., electrical power)inductively to a wireless power receiver 7002, which comprises asecondary coil 7004 connected to a load 7006.

The wireless power transmitter 7000 comprises a primary coil 7008, apower supply 7010 and an associated driver 7012, a monitoring system7014, a controller 7016, and one or more memory modules 7018, which maycomprise at least one of volatile and non-volatile memory.

The primary coil 7008 is configured to be inductively, loosely, tightly,remotely coupled or otherwise associated with the secondary coil 7004for transmitting power thereto, according to any suitable method, manywhich are well-known in the art.

The driver 7012 is configured to provide a varying electric potentialfrom the power supply 7010 to the primary coil 7008.

The monitoring system 7014 is configured to measure (directly orindirectly) electrical flow parameters of the primary coil 7008. Theelectrical flow parameters may include the voltage and/or current acrossthe primary coil 7008. As such, the monitoring system 7014 may comprisea voltage monitor 7020 configured to measure the voltage across theprimary coil 7008, and a current monitor 7022 configured to measure thecurrent across the primary coil. It will be noted that while the voltageand current monitors 7020, 7022 are illustrated schematically as beingdistinct element, a single element may be provided which performs thefunctions of both without departing from the scope of the presentdisclosure, mutatis mutandis.

The controller 7016, which may comprise or be constituted by amicrocontroller, is configured to detect, based on the electrical flowparameters measured by the monitoring system 7014, an error condition.The error condition may be indicative of a foreign object introducedbetween the primary coil and the secondary coil, which affects therelationship among at least some of the electrical flow parameters. Thecontroller 7016 is configured to facilitate interrupting the electricalpotential to the primary coil, for example when the error condition isdetected.

It will be appreciated that while FIG. 8 illustrates controlrelationships (in broken lines) between the controller 7016 and otherelements of the wireless power transmitter 7000, these are by way ofillustration only and are non-limiting. One skilled in the art willrecognize that other control relationships may exist, and those shownmay not exist in practice, mutatis mutandis.

The electrical potential may be interrupted in any convenient fashion.According to some examples, the controller 7016 may direct the powersupply 7010 and/or driver 7012 to stop the supply of power. According toother examples, the wireless power transmitter 7000 may comprise acircuit breaker 7024, which is configured to selectivelyconnect/disconnect the power supply 7010 to/from the primary coil 7008.This may be useful, for example, when a single power supply 7010 is usedto simultaneously provide power to multiple primary coils 7008, therebyallowing the electrical potential to each primary coil to be interruptedwithout affecting the supply to the other ones.

In addition, a signal conditioner 7026 may be provided, downstream ofthe monitoring system 7014, configured to produce a signal from which anerror condition may be more easily detected. For example, it maycomprise a frequency changer 7028 configured to increase the frequencyof an output signal of the monitoring system. Furthermore, it maycomprise a filter 7030, such as a Butterworth filter, configured toreduce noise of the output signal.

The controller 7016 may be configured to carry out one of one or moremethods to detect an error condition. In order to accomplish this, e.g.,reference parameters, indicative of either an error condition or of anon-error condition, are compared to values measured by the monitoringsystem 7014. In order to facilitate this, the controller 7016 maycomprise a comparator 7032.

According to some examples, the controller 7016 is configured tocalculate reference parameters of one or more of the electrical flowparameters. The frequency of the input signal, i.e., of the electricpotential provided by the driver 7012, may also be taken into accountwhen calculating the reference parameters. According to other examples,reference parameters used by the controller 7016 are provided inadvance, e.g., stored in the volatile or non-volatile memory of thememory module 7018.

The wireless power transmitter 7000 may be configured to perform one ormore type of foreign object tests to detect an error condition. Asillustrated in FIG. 9, a startup foreign object test, generallyindicated at 7100, may be performed as follows (it will be appreciatedthat while elements of the wireless power transmitter which perform someof the steps are listed, it is by way of example only, and some of thesteps may be performed by elements other than those listed withoutdeparting from the scope of the presently disclosed subject matter,mutatis mutandis):

-   -   In step 7102, the frequency of the varying electrical potential        through a plurality of frequencies from a first frequency to a        second frequency is decreased.    -   In step 7104, the controller 7016 determines a threshold value        for each of one or more of the electrical flow parameters (for        example the voltage and current across the primary coil 7008)        for at least some of the plurality of frequencies, the threshold        values corresponding to non-error conditions and constituting        one of the reference parameters.    -   In step 7106, the monitoring system 7014 monitors the electrical        flow parameters.    -   In step 7108, the error condition is detected by the controller        7016 if one or more of the electrical flow parameters exceeds        the threshold value.

Startup foreign object test 7100 may be particularly useful, forexample, when charging is initiated, i.e., during a so-called “softstart”.

As illustrated in FIG. 10, a transmission foreign object test, generallyindicated at 7120, may be performed as follows (it will be appreciatedthat while elements of the wireless power transmitter which perform someof the steps are listed, it is by way of example only, and some of thesteps may be performed by elements other than those listed withoutdeparting from the scope of the presently disclosed subject matter,mutatis mutandis):

-   -   In step 7122, a relationship between two or more of the        electrical flow parameters is determined. The relationship may        be based on at least the voltage and current across the primary        coil. The relationship may be further based on the frequency of        the varying electrical potential.    -   In step 7124, a threshold value for the relationship,        corresponding to a non-error condition and constituting the        reference parameters, is determined.    -   In step 7126, the monitoring system monitors the electrical flow        parameters.    -   In step 7128, a measured relationship of the measured electrical        flow parameters is calculated.    -   In step 7130, the error condition is detected if the measured        relationship is beyond the threshold value.

The detection in step 7130 is based on the finding that the ratiobetween peak DC voltage and the current is always above a certainthreshold value in the case of an error condition (i.e., if there is aforeign object between the wireless power transmitter and the wirelesspower receiver), and below it when an error condition does not exist.This relationship may take the driving frequency of the varying electricpotential into account.

As illustrated in FIG. 11, an idle foreign object test, generallyindicated at 7140, may be performed as follows (it will be appreciatedthat while elements of the wireless power transmitter which perform someof the steps are listed, it is by way of example only, and some of thesteps may be performed by elements other than those listed withoutdeparting from the scope of the presently disclosed subject matter,mutatis mutandis):

-   -   In step 7142, a calibration ping signal is transmitted at a time        when it is known that the error condition does not exist. This        may be done, for example, during manufacture.    -   In step 7144, the signal decay time of the calibration ping        signal is measured and recorded, for example in non-volatile        memory of the memory module 7018.    -   In step 7146, a test ping signal is transmitted, and the signal        decay time thereof is recorded.    -   In step 7148, an error condition is detected if the signal decay        time of the test ping signal is below the signal decay time of        the calibration ping signal, beyond a predetermined threshold.

It will be appreciated that the signal decay time may be obtained in anysuitable fashion without departing from the scope of the presentlydisclosed subject matter, mutatis mutandis. For example, it may betransmitted thereto from an external source, for example taking intoaccount environment conditions (parameters of a charging surface, etc.)

The foreign object test 7140 may be modified by recording the peakvoltage and/or current during a ping, mutatis mutandis. In this respect,it will be appreciated that a small electric potential may be providedto the primary coil 7008 for the purpose of the foreign object test 7140is necessary.

It is further noted that perturbations in the self-resonance of thesystem may indicate the presence of a foreign body. Accordingly,self-resonance of the system may be determined at intervals such thatany perturbations may be detected indicating the possible presence ofsuch foreign objects.

The idle foreign object test 7140 may be particularly useful, forexample, when the wireless power transmitter is in an idle state, i.e.,while it is not engaged in power transfer.

With regard to detection of perturbations in the self-resonance of thesystem, as illustrated in FIG. 12, another example of a wireless powertransmitter, which is generally indicated at 8000, is provided. Thewireless power transmitter 8000 is configured to transmit power (e.g.,electrical power) inductively or otherwise wirelessly to a wirelesspower receiver 8002, which comprises a secondary coil 8004 connected toa load 8006.

The wireless power transmitter 8000 comprises a primary coil 8008, apower supply 8010 and an associated driver 8012, a monitoring system8014, a controller 8016, and one or more memory modules 8018, which maycomprise at least one of volatile and non-volatile memory.

The primary coil 8008 is configured to be inductively coupled to thesecondary coil 8004 thereby forming an inductive couple therewith, or tootherwise to transfer power thereto according to any suitable method,many which are well-known in the art.

The driver 8012 is configured to provide a varying electric potentialfrom the power supply 8010 to the primary coil 8008. The electricalpotential may vary, e.g., based on feedback from the secondary coil8004.

The monitoring system 8014 is configured to measure (directly orindirectly) electrical flow parameters of the primary coil 8008. Theelectrical flow parameters may relate to the voltage and/or currentacross the primary coil 8008, and may include, but are not limited to,the frequency and/or amplitude thereof. As such, the monitoring system8014 may comprise a voltage monitor 8020 configured to measure thevoltage across the primary coil 8008, and a current monitor 8022configured to measure the current across the primary coil. It will benoted that while the voltage and current monitors 8020, 8022 areillustrated schematically as being distinct element, a single elementmay be provided which performs the functions of both without departingfrom the scope of the present disclosure, mutatis mutandis. In addition,it is configured to filter the measured electrical flow parameters basedon a set of filter characteristics, thereby producing a response signal.

The controller 8016, which may comprise or be constituted by amicrocontroller, is configured to direct operation of the wireless powertransmitter 8000, i.e., the operation of its components. It isconfigured, inter alia, to perform error checking, for example todetect, e.g., based on the electrical flow parameters measured by themonitoring system 8014, an error condition. The error condition may beindicative of a foreign object introduced between the primary coil andthe secondary coil, which affects the relationship among at least someof the electrical flow parameters. In order to facilitate the errorchecking, the controller 8016 may comprise a comparator 8032, as will bedescribed below.

The controller 8016 may be further configured to facilitate interruptingthe electrical potential to the primary coil, for example when the errorcondition is detected.

According to one example, as illustrated in FIG. 13, the error checkingmay comprise a method 8100, with the following steps:

-   -   In step 8102, the controller 8016 directs the driver 8012 to        provide the electric potential as a signal being a superposition        of a transmission signal, which is for transmission of power to        the wireless power receiver 8002, and of a sensing signal.    -   In step 8104, the monitoring system 8014 measures electrical        flow parameters of the primary coil 8008.    -   In step 8106, the monitoring system 8014 produces a response        signal by filtering the measured electrical flow parameters        based on a set of filter characteristics which characterize the        transmission signal.    -   In step 8108, the controller 8016 compares, e.g., using the        comparator 8032, one or more electrical flow parameters of the        response signal on the one hand, and on the other hand        corresponding electrical flow parameters of the sensing signal.    -   In step 8110, the controller 8016 determines, based on the        comparison of step 8108, whether or not an error condition such        as a foreign object exists between the primary and secondary        coils 8008, 8004. If the compared characteristics of the        response signal are determined by the controller 8016 to be        about the same as those of the sensing signal response, it may        determine that no such error condition exists, as changes in the        electrical flow parameters (measured by the monitoring system in        step 8104) which are due to operation of the secondary wireless        power receiver 8002 will not affect the sensing signal. If the        compared characteristics of the response signal are determined        by the controller 8016 to be substantially different, the        controller 8016 may determine that an error condition (such as a        foreign object between the primary and secondary coils 8008,        8004) exists, and take suitable action (e.g., interrupting the        electrical potential to the primary coil).

According to some modifications, the error checking is performed in anongoing manner during power transmission to the wireless power receiver8002. According to various modifications, error checking may beperformed continuously or at intervals (e.g., once every second) asdeemed appropriate by the designer to be sufficient to protect againstdamage by foreign objects.

The sensing signal may be substantially different from the transmissionsignal, for example having a frequency which is not in the range thatthe transmission signal typically varies within. By way of example thefrequency of the sensing signal may be much higher or much lower thanthe frequency of the transmission signal. The frequency of thetransmission signal may be of a constant frequency, which may facilitatethe filter characteristics to be hardwired into the monitoring system8014.

One skilled in the art will appreciate that the difference between thecompared characteristics of the response and sensing signals thatindicate an error condition may depend on several factors, and willdesign the wireless power transmitter 8000 accordingly. In addition, hewill appreciate how different the sensing signal should be from therange of the transmission signal in order to ensure efficientmonitoring, and will design the wireless power transmitter 8000accordingly.

It will be appreciated that while FIG. 8 illustrates controlrelationships (in broken lines) between the controller 8016 and otherelements of the wireless power transmitter 8000, these are by way ofillustration only and are non-limiting. One skilled in the art willrecognize that other control relationships may exist, and those shownmay not exist in practice, mutatis mutandis.

The electrical potential may be interrupted in any suitable fashion.According to some examples, the controller 8016 may direct the powersupply 8010 and/or driver 8012 to stop the supply of power. According toother examples, the wireless power transmitter 8000 may comprise acircuit breaker 8024, which is configured to selectivelyconnect/disconnect the power supply 8010 to/from the primary coil 8008.This may be useful, for example, when a single power supply 8010 is usedto simultaneously provide power to multiple primary coils 8008, therebyallowing the electrical potential to each primary coil to be interruptedwith affecting the supply to the other ones.

As illustrated in FIG. 14, an wireless charging station, which isgenerally indicated at 9000, may be provided, to assist in detection offoreign objects. The wireless charging station 9000 may, e.g.,integrated into a charging surface. The wireless charging station 9000comprises a wireless power transmitter 9002, a metal detecting array9004, and a controller 9006.

The wireless power transmitter 9002 may be provided according to anysuitable design, many of which are known in the art. For example, it maycomprise a primary coil 9008, which is capable of being inductivelycoupled to a secondary coil, and a power supply having an associatedriver (both not shown in FIG. 12) configured to provide a varyingelectrical potential from the power supply to the primary coil.According to some examples, the wireless power transmitter 9002 isprovided in accordance with that described above with reference to FIGS.8 through 11. The controller 9006 may be configured to work with, or mayconstitute a part of, the controller 7016 described above with referenceto FIGS. 8 through 11.

The metal detecting array 9004 comprises a plurality of metal detectors9010, each of which may be provided according to any suitable design,many of which are known in the art. For example, each of the metaldetectors may comprise a metal detector coil 9012. The metal detectors9010 are arranged symmetrically around the wireless power transmitter9002. It will be noted in this regard that the wireless powertransmitter 9002 does not need to be arranged symmetrically with themetal detectors 9010, e.g., it may be eccentrically positionedtherebetween. According to some examples, the metal detecting array 9004comprises an even number (i.e., 2, 4, 6, etc.) of metal detectors 9010.

The metal detecting array 9004 may comprise an oscillator 9014,configured to produce an alternating current passing through each of thedetector coils 9012, thereby producing the magnetic field. It will beappreciated that while the oscillator 9014 is connected to each of thedetector coils 9012, it is only illustrated as being connected to one ofthem. It addition, it will be appreciated that a single oscillator 9014may be provided for the entire metal detecting array 9004, or more thanone, with each oscillator being connected to one or more of the metaldetecting coils.

The controller 9006 is configured to detect a foreign object in thevicinity of the metal detecting array 9004, based on a change in amagnetic field of at least one of the detector coils 9012, which isindicative of the presence of a metal object in the vicinity. Accordingto some examples, the controller 9006 is configured to detect theforeign object by the comparing the changes in the magnetic fields ofthe coils. The detecting may thus be based on a differential in thechanges of different detector coils. This allows the metal detectingarray 9004 to be used to detect small metal objects. It may additionallybe configured to interrupt the supply of power via the primary coil9008, for example by interrupting power supply thereto.

It will be appreciated that while herein the specification and claims,the term “controller” may be used as if in reference to a singleelement, it may refer to a combination of elements, which may or may notbe in physical proximity to one another, without departing from thescope of the presently disclosed subject matter, mutatis mutandis. Inaddition, disclosure herein (including recitation in the appendedclaims) of a controller carrying out, being configured to carry out, orother similar language, implicitly includes other elements carrying out,being configured to carry out, etc., those functions, without departingfrom the scope of the presently disclosed subject matter, mutatismutandis.

Thus a number of related technologies are presented that use signaltransfer systems across a wireless power coupling to regulate the powerand to detect and align the two coils.

The scope of the present invention is defined by the appended claims andincludes both combinations and sub combinations of the various featuresdescribed hereinabove as well as variations and modifications thereof,which would occur to persons skilled in the art upon reading theforegoing description.

Those skilled in the art to which this invention pertains will readilyappreciate that numerous changes, variations and modifications can bemade without departing from the scope of the invention mutatis mutandis.

Technical and scientific terms used herein should have the same meaningas commonly understood by one of ordinary skill in the art to which thedisclosure pertains. Nevertheless, it is expected that during the lifeof a patent maturing from this application many relevant systems andmethods will be developed. Accordingly, the scope of the terms such ascomputing unit, network, display, memory, server and the like areintended to include all such new technologies a priori.

The terms “comprises”, “comprising”, “includes”, “including”, “having”and their conjugates mean “including but not limited to” and indicatethat the components listed are included, but not generally to theexclusion of other components. Such terms encompass the terms“consisting of” and “consisting essentially of”.

The phrase “consisting essentially of” means that the composition ormethod may include additional ingredients and/or steps, but only if theadditional ingredients and/or steps do not materially alter the basicand novel characteristics of the composition or method.

As used herein, the singular form “a”, “an” and “the” may include pluralreferences unless the context clearly dictates otherwise. For example,the term “a compound” or “at least one compound” may include a pluralityof compounds, including mixtures thereof.

The word “optionally” is used herein to mean “is provided in someembodiments and not provided in other embodiments”. Any particularembodiment of the disclosure may include a plurality of “optional”features unless such features conflict.

Whenever a numerical range is indicated herein, it is meant to includeany cited numeral (fractional or integral) within the indicated range.The phrases “ranging/ranges between” a first indicate number and asecond indicate number and “ranging/ranges from” a first indicate number“to” a second indicate number are used herein interchangeably and aremeant to include the first and second indicated numbers and all thefractional and integral numerals therebetween. It should be understood,therefore, that the description in range format is merely forconvenience and brevity and should not be construed as an inflexiblelimitation on the scope of the disclosure. Accordingly, the descriptionof a range should be considered to have specifically disclosed all thepossible subranges as well as individual numerical values within thatrange. For example, description of a range such as from 1 to 6 should beconsidered to have specifically disclosed subranges such as from 1 to 3,from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., aswell as individual numbers within that range, for example, 1, 2, 3, 4,5, and 6 as well as non-integral intermediate values. This appliesregardless of the breadth of the range.

It is appreciated that certain features of the disclosure, which are,for clarity, described in the context of separate embodiments, may alsobe provided in combination in a single embodiment. Conversely, variousfeatures of the disclosure, which are, for brevity, described in thecontext of a single embodiment, may also be provided separately or inany suitable subcombination or as suitable in any other describedembodiment of the disclosure. Certain features described in the contextof various embodiments are not to be considered essential features ofthose embodiments, unless the embodiment is inoperative without thoseelements.

Although the disclosure has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the disclosure.

All publications, patents and patent applications mentioned in thisspecification are herein incorporated in their entirety by referenceinto the specification, to the same extent as if each individualpublication, patent or patent application was specifically andindividually indicated to be incorporated herein by reference. Inaddition, citation or identification of any reference in thisapplication shall not be construed as an admission that such referenceis available as prior art to the present disclosure. To the extent thatsection headings are used, they should not be construed as necessarilylimiting.

1. A wireless power transmitter for power transmission to a wirelesspower receiver, the wireless power transmitter comprising: a primarycoil to transfer power to a secondary coil of said wireless powerreceiver; a power supply; a driver to provide an electric potential fromsaid power supply to said primary coil; a monitoring system to measureelectrical flow parameters of said primary coil, and to filter themeasured electrical flow parameters based on one or more filtercharacteristics, thereby producing a response signal; and a controllerto direct operation of the wireless power transmitter, wherein thecontroller is configured to perform error checking by: directing saiddriver to provide said electric potential as a superposition of atransmission signal and a sensing signal, said filter characteristicscomprising electrical flow parameters of one of said transmission andsensing signals; and detecting, based a difference between one or moreelectrical flow parameters of said response signal and of the other ofsaid transmission and sensing signals, an error condition indicative ofa foreign object between said primary and secondary coils.
 2. Thewireless power transmitter according to claim 1, wherein the frequencyof said sensing signal is substantially different from the frequency ofsaid transmission signal.
 3. The wireless power transmitter according toclaim 1, wherein said filter characteristics comprise electrical flowparameters of said transmission signal.
 4. The wireless powertransmitter according to claim 1, wherein the frequency of said sensingsignal is constant.
 5. The wireless power transmitter according to claim1, wherein said controller is configured to vary the frequency of saidtransmission signal during the power transmission.
 6. The wireless powertransmitter according to claim 1, wherein said controller is furtherconfigured to facilitate, when said error condition is detected,interrupting said electrical potential to said primary coil.
 7. Thewireless power transmitter according to claim 6, wherein thefacilitating comprises directing said driver to cease providing saidelectric potential.
 8. The wireless power transmitter according to claim1, wherein said controller is configured to perform said error checkingin an ongoing manner during the power transmission.
 9. The wirelesspower transmitter according to claim 1, wherein said controller isconfigured to perform said error checking at intervals during the powertransmission.
 10. The wireless power transmitter according to claim 1,wherein said controller comprises a comparator.
 11. A method ofdetecting an error condition, indicative of a foreign object between awireless power transmitter and a wireless power receiver, said wirelesspower transmitter comprising a primary coil for transferring powerwirelessly to a secondary coil of said wireless power receiver, themethod comprising: providing an electric potential, being asuperposition of a transmission signal and a sensing signal, to saidprimary coil; measuring electrical flow parameters of said primary coil;filtering the measured electrical flow parameters based on one or morefilter characteristics, thereby producing a response signal; comparingone or more electrical flow parameters of the response signal withcorresponding electrical flow parameters of one of said transmission andsensing signals; and determining, based on said comparing, whether ornot said error condition exists.
 12. The method according to claim 11,wherein the frequency of said sensing signal is substantially differentfrom the frequency of said transmission signal.
 13. The method accordingto claim 11, wherein said filter characteristics comprise electricalflow parameters of said transmission signal.
 14. The method according toclaim 11, wherein the frequency of said sensing signal is constant. 15.The method according to claim 11, wherein the frequency of saidtransmission signal varies during the power transmission.
 16. The methodaccording to claim 11, further comprising, when said error condition isdetected, interrupting said electrical potential to said primary coil.17. The method according to claim 11, wherein said error checking isperformed in an ongoing manner during the power transmission.
 18. Themethod according to claim 11, wherein said error checking is performedcontinuously during the power transmission.
 19. The method according toclaim 11, wherein said error checking is performed at intervals duringthe power transmission.
 20. The method according to claim 11, whereinsaid wireless power transmitter further comprises a comparator.